Traditional paper clips have a major advantage in that they are very cheap to manufacture. Hundreds, if not thousands, of them can be purchased for less than a dollar. However, they have certain disadvantages. First, because there is always a wire end against the paper, there is a tendency for the clip to tear the paper when it is removed. Secondly, once the clip is in place, it is not always clear when looking at a stack of papers, where the paper clip is. It might be necessary, for example, to move a certain group of papers that have been clipped together, but the irregular edges of the papers in the stack make is impossible where the clip is.
Lastly, the typical paper clip has a tendency to be bent out of shape on the first use, making it a nuisance to use.